1. Field of the Invention
The present invention relates to a technology for controlling a cooling unit that cools a heat-producing unit in an apparatus.
2. Description of the Related Art
In general, if a user does not operate an image processing apparatus, such as a printer, a copier, or a multifunction product (MFP), for a predetermined time, an operating state of the image processing apparatus is shifted to an energy-saving state. In the energy-saving state, the image processing apparatus causes some functions to be maintained in an operable state and the other functions to be stopped, and cuts off power for corresponding circuits to reduce the power consumption.
In recent years, the image processing apparatus includes a controller having a device with high processing performance, such as a central processing unit (CPU) and an application specific integrated circuit (ASIC), to achieve multiple functions with high performance. Because such a device generates a large amount of heat, if an appropriate cooling operation is not performed on the device, thermal runaway can occur in the device, resulting in a false operation or a breakdown of the device.
When the operating state of the image processing apparatus is shifted to the energy-saving state, the power is cut off for devices excluding some essential circuits such as a controller ASIC that monitors a factor (return factor) for returning to a normal operating state. Therefore, operations of a fan that exhausts high-temperature air from inside of a controller box that accommodates the controller (hereinafter, “case fan”) and a fan that cools a substrate on which the CPU is mounted (hereinafter, “CPU fan”) are stopped.
If the device and the controller box are overheated, a temperature of the device can exceed a limit of operating temperature of the device, causing thermal runaway in a currently-operating device.
To solve the above problem, Japanese Patent Application Laid-open No. 2004-163628 discloses an image forming apparatus that controls an operation of a fan that cools the image forming apparatus depending on an amount of operations performed by the image forming apparatus. A time at which the operating state is shifted to the energy-saving state in which the fan cannot be driven is changed based on the detected amount of operations. Specifically, if the amount of operations is large, a time during which the image forming apparatus is in a standby state to drive the fan is extended, so that the fan can be driven for a longer time.
With the method disclosed in Japanese Patent Application Laid-open No. 2004-163628, it is possible to prevent a situation where the fan cannot be driven due to the high temperature because the operating state is shifted to the energy-saving state even though the image forming apparatus is not sufficiently cooled down. However, because the method is based on an extended standby state where the power is still supplied to the controller and each processing unit for forming an image, the power is unnecessarily consumed and the energy-saving efficiency is degraded.